um, let you move around and whip things in first person?
also, expand Henry's game to use all stages. i think it'd be fun if they somewhat randomized the locations of the children and the levels that they're hidden in so that you could replay it and never quite know for sure where they'll be.
have a stage select mode, but let characters who normally don't play that stage play them using it. i have great memories using cheat devices in order to do that. while you're at it, let you choose which layout you want to play for a stage (LoD version or original version) while still using the LoD versions of the characters.
if they don't do an all out next-gen graphical remake, at least make the enhanced graphics mode look better.
i don't ever want to do the Mandragora/Magical Nitro thing again (I tend to stop playing when I get to that point in a replay). at least offer some kind of secret shortcut that allows you to bypass the most difficult part of that challenge.
make a version of Cornell more of a melee fighter as it seems he was originally meant to be. give him the dang ability to turn off his wolf powers. heck, for giggles, let his wolf form play much the same as he did in Judgment (though he can lose the armor).
speaking of Judgment, clear up the storyline to make it easier to reconcile the two games.
bring in a full mode for Coller and come up with some neat way to make his game different than Henry and explain the relationship between him and the Gardener. at the very least, offer him as an "Alternate Costume" for Henry.
for super giggles, let you play the game through as Charles Vincent.